The present invention relates to cutting inserts and, more particularly, to cutting inserts having evolutive wedge and/or clearance angles.
When using rotating tools with circular cutting inserts to cut material, it is common to form the cutting insert in the form of a truncated cone. The edge of the large end of the cone typically forms the “top” of the insert, and the periphery of the top forms a cutting edge that contacts a workpiece. The cone angle, i.e., the angle between a reference plane through the top of the insert and the conical side, is typically referred to as the clearance angle of the insert. As the tool rotates, the side of the cone “follows” the cutting edge. Often, the insert is arranged at an angle to an axis of rotation and/or at an angle to a radius of the tool to facilitate use of the sharp corner or wedge angle between the top and the conical side of the insert. This typically entails tilting the insert so that the conical side of the inert is closer to the material that has just been cut by the cutting edge that it follows. While providing a narrow wedge angle will often make it easier to cut material, it will often be at the expense of strength of the cutting edge.
U.S. Pat. No. 5,725,334A discloses a circular cutting insert including a negative land 27 that varies in size around the cutting edge. The land 27 appears to form a constant, non-varying angle with the frustoconical clearance surface below the land. There is no disclosure regarding a wedge angle between a surface interior of the land 27 and the clearance surface.
DE10006431C1 discloses a circular cutting insert having a protective bevel (1) that varies in size at different points around the cutting edge.
DE19855103A1 discloses a circular cutting insert having a protective bevel 2 that varies in size at different points around the cutting edge.
EP1964631A2 discloses a circular cutting insert 1 having a top surface 2, a cutting edge 5, and clearance surface 4. The document discloses that the clearance surface may be divided into several sections, which have a different inclination relative to the base 3 and the deck surface 2, such that, at different heights of the clearance surface between the base 3 and deck 2, the clearance surface can form different angles. Such a configuration is common in cutting inserts.
U.S. Patent App. Pub. US2007/0189863A1 discloses a circular cutting insert and shows, in FIGS. 6A-6C, an insert with a cutting edge C47 that varies in height relative to a bottom of the insert around the circumference of the insert.
It is desirable to provide an insert that both facilitates cutting of a workpiece while also providing substantial cutting edge strength.
According to an aspect of the present invention, an indexable circular cutting insert includes including a land surface adjacent to a top surface including a top edge portion, a side surface including a clearance surface and a clearance edge portion, and a cutting edge defined by an intersection of the clearance edge portion and the land surface. The clearance edge portion and the top edge portion form a wedge angle. The wedge angle varies as a function of circumferential position about a central axis of the insert relative to a point on the cutting edge. The cutting insert is indexable to a plurality of different indexing positions. The wedge angle varies between a maximum and a minimum value as a function of circumferential position about the central axis of the insert relative to a point on the cutting edge corresponding to each indexing position.